1. Field of the Invention
The invention relates to antibodies capable of binding to tissue factor, without inhibiting normal tissue factor mediated blood coagulation, and methods of making and methods of use thereof, including in the treatment of cancer.
2. Related Art
Tissue factor (TF) is a cell-anchored component that, together with factor VIIa, initiates blood coagulation in vivo. TF is a transmembrane glycoprotein with a 219 amino acid residue extracellular region, a 23 amino acid residue transmembrane region and a 21 amino acid residue cytoplasmic region. The extracellular region of TF has two fibronectin III-like domains and a distribution of disulfide bridges characteristic of class-II cytokine and interferon receptors. The cytoplasmic region of TF is short but contains at least one serine residue that can be phosphorylated.
Tissue factor forms a tight complex (Kd˜pmol) with its native ligand—factor VIIa. In the complex, VIIa wraps around tissue factor (Banner, D. W., et al., Nature 380:41-46 (1996)) and forms an extensive region of contact with the tissue factor surface.
Patients with cancer exhibit a much higher than expected incidence of thromboembolic disorders, commonly referred to as Trousseau syndrome. Many tumor types commonly associated with Trousseau syndrome, such as lung, pancreatic, breast, colon, and gastric carcinomas, stain positively for TF (Hu, T., et al., Oncol. Res. 6:321-327 (1994); Callander, N. S., et al., Cancer 70:1194-201 (1992)). Abnormally high expression of TF has been shown clinically to be associated with poor differentiation of many tumors, including colorectal carcinoma (Shigemori, C., et al., Thromb. Haemost. 80:894-898 (1998); Seto, S., et al., Cancer 88:295-301 (2000)); and non-small cell lung cancer (Sawada, M., et al., Br. J. Cancer 79:472-477 (1999)). Molecular analysis of gene expression shows that TF is differentially expressed in breast cancer cells (Kirschmann, D. A., et al., Breast Cancer Res. Treat. 55:127-136 (1999); Schwirzke, M., et al., Anticancer Res. 19:1801-1814 (1999)).
In tumor tissues, TF is not only expressed on the surface of tumor cells but also on tumor associated vascular endothelial cells. TF has been shown to play an essential role in embryonic blood vessel development (Carmeliet, P., et al., Nature 383:73-75 (1996)). TF normally is not expressed in the endothelium. However, tumor associated vascular endothelial cells in breast cancer (Contrino, J., et al., Nat. Med. 2:209-215 (1996); Shoji, M., et al., Am. J. Pathol. 152:399-411 (1998)), pituitary adenoma (Nishi, T., et al., Cancer 86:1354-1361 (1999)) and lung cancer (Shoji, M., et al., Am. J. Pathol. 152:399-411 (1998); Koomagi, R. and Vohm, M., Int. J. Cancer 79:19-22 (1998)) have been shown to express TF. The expression of TF by tumor cells and tumor associated vascular endothelial cells was shown to be induced by tumor secreted VEGF and TNF (Bierhaus, A., et al., J. Biol. Chem. 270:26419-26432 (1995); Zucker, S., et al., Int. J. Cancer 75:780-786 (1998); Shen, B. Q., et al., J. Biol. Chem. 276:5281-5286 (2001)).
In normal tissue, TF is only expressed in cells separated from blood proteins by tight endothelium and tissue barriers such as skin, and TF is normally not readily accessible to blood proteins and antibodies. However, in tumor tissues, TF of tumor associated vascular endothelial cells is exposed to blood proteins. At the same time, tumor TF is also accessible because of the leaky tumor vasculature. Tumor cells secrete matrix metalloproteases that most likely play a role in the invasion process, and may be a cause of the leakiness.
Antibodies that bind to the TF-VIIa interaction site can inhibit TF-VIIa interaction, thus inhibiting or blocking blood coagulation. However, when large quantities of those antibodies are used for tumor therapy, effective bleeding control in patients may be compromised.